Shock absorbers are used with automobiles and other vehicles to absorb shock forces sustained by the vehicle wheels. One type of shock absorber used in such applications is the conventional, linear-style shock absorber. Linear-style shock absorbers typically include a pair of telescoping cylindrical sleeves oriented generally vertically in the vehicle. A piston associated with one of the sleeves travels in a fluid-filled cylinder associated with the other sleeve. One end of the shock absorber is coupled to a wheel support structure and the other end is fixed to the body or frame of the vehicle. When a shock force displaces one of the vehicle wheels, the force drives the piston along the cylinder, thereby driving fluid through an orifice in the piston. The piston resists such motion with a force proportional to the shock force. Such linear shock absorbers must be oriented substantially vertically within the vehicle body and must be positioned adjacent the associated vehicle wheel.
Rotary shock absorbers, also known as rotary dampers, have been developed to replace linear-style shock absorbers. Rotary shock absorbers operate by converting shock forces into rotary motion, and then damping the rotary motion. Rotary shock absorbers have several advantages over conventional linear-style shock absorbers. For example, rotary shock absorbers do not need to be mounted adjacent to the vehicle wheel, as do linear-type shock absorbers, nor do they need to be mounted in any particular orientation. Rotary dampers may be oriented generally horizontally, and thereby extend underneath the body of the vehicle.
Rotary dampers typically include a shaft which transmits shock forces from the wheel to one or more rotors encased in a cylindrical housing. Each rotor preferably includes two or more lobes and the housing includes ported guide plates between the lobes. The housing contains fluid in the gap between the lobes and guide plates. When the rotor is rotated, the fluid is compressed by the rotor against the guide plates and is forced through the ports in the guide plates. Typically, there arc seals between the rotor and the housing and the rotor and the guide plates which restrict the flow of damping fluid around the rotor, and such seals require close tolerances to be effective. However, repeated oscillations of the rotor wear the mechanical seals and eventually require replacement of the damper. Accordingly, there is a need for a rotary damper which has effective, durable, and inexpensive flow-restricting seals between the rotor and the housing and guide plates.